Note 11 - Stockholders' Equity - Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2023	Mar. 31, 2022
Foreign currency translation adjustment attributable to Verisk, before tax		$ 59.3	$ (71.0)
Foreign currency translation adjustment attributable to Verisk, tax		0.0
Foreign currency translation adjustment attributable to Verisk, after tax		59.3	(71.0)
Foreign currency translation adjustment attributable to noncontrolling interests, before tax		(0.7)	(0.6)
Foreign currency translation adjustment attributable to noncontrolling interests, tax		0.0	0.0
Foreign currency translation adjustment attributable to noncontrolling interests, after tax		(0.7)	(0.6)
Cumulative translation adjustment recognized upon deconsolidation, before tax		700.6
Cumulative translation adjustment recognized upon deconsolidation , tax		0.0
Cumulative translation adjustment recognized upon deconsolidation, after tax		700.6
Foreign currency translation adjustment, before tax		759.2	(71.6)
Foreign currency translation adjustment, tax		0.0	0.0
Foreign currency translation adjustment, after tax		759.2	(71.6)
Total other comprehensive income, before tax		760.2	(71.0)
Total other comprehensive income, tax		(0.3)	0.0
Total other comprehensive income, after tax		759.9	(71.0)
Total other comprehensive loss, before tax		760.2	(71.0)
Total other comprehensive loss, tax		(0.3)	0.0
Pension and Postretirement Adjustment [Member]
Other comprehensive income (loss), before reclassifications, before tax		2.5	1.3
Other comprehensive income (loss), before reclassifications, tax		0.1	(0.2)
Other comprehensive income (loss), before reclassifications, after tax		2.6	1.1
Amortization of net actuarial loss and prior service benefit reclassified from accumulated other comprehensive income (losses), before tax	[1]	(1.5)	(0.7)
Amortization of net actuarial loss and prior service benefit reclassified from accumulated other comprehensive income (loss), tax	[1]	(0.4)	0.2
Amortization of net actuarial loss and prior service benefit reclassified from accumulated other comprehensive income (losses), after tax	[1]	(1.9)	(0.5)
Other comprehensive income (loss), before tax		1.0	0.6
Other comprehensive income (loss), tax		(0.3)	0.0
Other comprehensive income (loss), after tax		$ 0.7	$ 0.6

[1] These accumulated other comprehensive loss components, before tax, are included under "Cost of revenues" and "Selling, general and administrative" in our accompanying consolidated statements of operations. These components are also included in the computation of net periodic (benefit) cost (See Note 18. Pension and Postretirement Benefits for additional details).